From nobody Sun Feb 8 08:48:17 2026 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1B4C81FDE1D; Mon, 2 Dec 2024 11:14:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733138054; cv=none; b=oHS7A3m0e5rY+RPgLI8BxjZGFvuUB+sH/weqIdypotSgkNNZWDTi7YYyQ0UiQUpJGGybsUx8c0l6Dr+Wcx66Jgd3uLXPYcCZ5/VCK+ph399Wae4/VApCz+SMrINDzntVVX4UFRGm9iCf7sHuqmAd8IHqS4KtxQGstYPaX9aZwIY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733138054; c=relaxed/simple; bh=aC4gv9LFdAIY2rGIq8AETgI+PjO8g77BcvzLFwQuTdc=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=S8VrjLMBBMtV89EIKCU/+NKuW+oPf1d/j97j2hI3z9wTCirLFB1NwwjQ/ERlgMJpjwNrFjFqbooMhpXGtYhvp/vlW8ToKIh5y0au/tw5kSnw/4c2BUxkOjOE4KBlgOZp7ZcKwTWMPDEdC7+Cus2CW3vtHucZClEXC7YITPP74TQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=PprAYotv; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=4ATdEelw; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="PprAYotv"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="4ATdEelw" Date: Mon, 02 Dec 2024 11:14:08 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1733138049; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=p5qKxeqR9rjPDCzSJbwHbsdytosWufphrcr2lGL4L78=; b=PprAYotvkghNezIXzjoNS/V3nlPvNj+PRfSeyWOb+dHigBhesUGE4CkvkvfpjyJnHDUWu8 JHQjxqubI9ILk+RqaRZN8J1shxzMMd497s1S0j/WiukQguniGuIQw+/2xe5FaFWLip5tXZ F/uAf1QXUD3Ug6IoPm+4cX0XfCtzvu70ZZqpjzyxCEvgSw9WFYeQqeL0pPbWd/wwnHkBhU WtvYhfwTRZC75CvOUSyaTIGdxCD+15xPKc3qOcqRssFq/s90w9aRUFew/75NDkJJkRcQEy /45O2V6/GtoSWD7QhipkjihupMdBsqV2p612RONTu7fvmr5s7sJfr1p0VxCyZQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1733138049; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=p5qKxeqR9rjPDCzSJbwHbsdytosWufphrcr2lGL4L78=; b=4ATdEelwL3Y/3CLEdx8Uib0fVeGwWuxXtqtL460QPaCm97+xXz83CV10ok1sLf8AKy6P7w VTsJpnf5e+09aDBg== From: "tip-bot2 for Andrii Nakryiko" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: perf/core] uprobes: add speculative lockless VMA-to-inode-to-uprobe resolution Cc: Matthew Wilcox , Peter Zijlstra , Andrii Nakryiko , Oleg Nesterov , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20241122035922.3321100-3-andrii@kernel.org> References: <20241122035922.3321100-3-andrii@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <173313804816.412.16764384544456207666.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the perf/core branch of tip: Commit-ID: e0925f2dc4de2d8ba987392d3239e8edf88f8b96 Gitweb: https://git.kernel.org/tip/e0925f2dc4de2d8ba987392d3239e8edf= 88f8b96 Author: Andrii Nakryiko AuthorDate: Thu, 21 Nov 2024 19:59:22 -08:00 Committer: Peter Zijlstra CommitterDate: Mon, 02 Dec 2024 12:01:38 +01:00 uprobes: add speculative lockless VMA-to-inode-to-uprobe resolution Given filp_cachep is marked SLAB_TYPESAFE_BY_RCU (and FMODE_BACKING files, a special case, now goes through RCU-delated freeing), we can safely access vma->vm_file->f_inode field locklessly under just rcu_read_lock() protection, which enables looking up uprobe from uprobes_tree completely locklessly and speculatively without the need to acquire mmap_lock for reads. In most cases, anyway, assuming that there are no parallel mm and/or VMA modifications. The underlying struct file's memory won't go away from under us (even if struct file can be reused in the meantime). We rely on newly added mmap_lock_speculate_{try_begin,retry}() helpers to validate that mm_struct stays intact for entire duration of this speculation. If not, we fall back to mmap_lock-protected lookup. The speculative logic is written in such a way that it will safely handle any garbage values that might be read from vma or file structs. Benchmarking results speak for themselves. BEFORE (latest tip/perf/core) =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D uprobe-nop ( 1 cpus): 3.384 =C2=B1 0.004M/s ( 3.384M/s/cpu) uprobe-nop ( 2 cpus): 5.456 =C2=B1 0.005M/s ( 2.728M/s/cpu) uprobe-nop ( 3 cpus): 7.863 =C2=B1 0.015M/s ( 2.621M/s/cpu) uprobe-nop ( 4 cpus): 9.442 =C2=B1 0.008M/s ( 2.360M/s/cpu) uprobe-nop ( 5 cpus): 11.036 =C2=B1 0.013M/s ( 2.207M/s/cpu) uprobe-nop ( 6 cpus): 10.884 =C2=B1 0.019M/s ( 1.814M/s/cpu) uprobe-nop ( 7 cpus): 7.897 =C2=B1 0.145M/s ( 1.128M/s/cpu) uprobe-nop ( 8 cpus): 10.021 =C2=B1 0.128M/s ( 1.253M/s/cpu) uprobe-nop (10 cpus): 9.932 =C2=B1 0.170M/s ( 0.993M/s/cpu) uprobe-nop (12 cpus): 8.369 =C2=B1 0.056M/s ( 0.697M/s/cpu) uprobe-nop (14 cpus): 8.678 =C2=B1 0.017M/s ( 0.620M/s/cpu) uprobe-nop (16 cpus): 7.392 =C2=B1 0.003M/s ( 0.462M/s/cpu) uprobe-nop (24 cpus): 5.326 =C2=B1 0.178M/s ( 0.222M/s/cpu) uprobe-nop (32 cpus): 5.426 =C2=B1 0.059M/s ( 0.170M/s/cpu) uprobe-nop (40 cpus): 5.262 =C2=B1 0.070M/s ( 0.132M/s/cpu) uprobe-nop (48 cpus): 6.121 =C2=B1 0.010M/s ( 0.128M/s/cpu) uprobe-nop (56 cpus): 6.252 =C2=B1 0.035M/s ( 0.112M/s/cpu) uprobe-nop (64 cpus): 7.644 =C2=B1 0.023M/s ( 0.119M/s/cpu) uprobe-nop (72 cpus): 7.781 =C2=B1 0.001M/s ( 0.108M/s/cpu) uprobe-nop (80 cpus): 8.992 =C2=B1 0.048M/s ( 0.112M/s/cpu) AFTER =3D=3D=3D=3D=3D uprobe-nop ( 1 cpus): 3.534 =C2=B1 0.033M/s ( 3.534M/s/cpu) uprobe-nop ( 2 cpus): 6.701 =C2=B1 0.007M/s ( 3.351M/s/cpu) uprobe-nop ( 3 cpus): 10.031 =C2=B1 0.007M/s ( 3.344M/s/cpu) uprobe-nop ( 4 cpus): 13.003 =C2=B1 0.012M/s ( 3.251M/s/cpu) uprobe-nop ( 5 cpus): 16.274 =C2=B1 0.006M/s ( 3.255M/s/cpu) uprobe-nop ( 6 cpus): 19.563 =C2=B1 0.024M/s ( 3.261M/s/cpu) uprobe-nop ( 7 cpus): 22.696 =C2=B1 0.054M/s ( 3.242M/s/cpu) uprobe-nop ( 8 cpus): 24.534 =C2=B1 0.010M/s ( 3.067M/s/cpu) uprobe-nop (10 cpus): 30.475 =C2=B1 0.117M/s ( 3.047M/s/cpu) uprobe-nop (12 cpus): 33.371 =C2=B1 0.017M/s ( 2.781M/s/cpu) uprobe-nop (14 cpus): 38.864 =C2=B1 0.004M/s ( 2.776M/s/cpu) uprobe-nop (16 cpus): 41.476 =C2=B1 0.020M/s ( 2.592M/s/cpu) uprobe-nop (24 cpus): 64.696 =C2=B1 0.021M/s ( 2.696M/s/cpu) uprobe-nop (32 cpus): 85.054 =C2=B1 0.027M/s ( 2.658M/s/cpu) uprobe-nop (40 cpus): 101.979 =C2=B1 0.032M/s ( 2.549M/s/cpu) uprobe-nop (48 cpus): 110.518 =C2=B1 0.056M/s ( 2.302M/s/cpu) uprobe-nop (56 cpus): 117.737 =C2=B1 0.020M/s ( 2.102M/s/cpu) uprobe-nop (64 cpus): 124.613 =C2=B1 0.079M/s ( 1.947M/s/cpu) uprobe-nop (72 cpus): 133.239 =C2=B1 0.032M/s ( 1.851M/s/cpu) uprobe-nop (80 cpus): 142.037 =C2=B1 0.138M/s ( 1.775M/s/cpu) Previously total throughput was maxing out at 11mln/s, and gradually declining past 8 cores. With this change, it now keeps growing with each added CPU, reaching 142mln/s at 80 CPUs (this was measured on a 80-core Intel(R) Xeon(R) Gold 6138 CPU @ 2.00GHz). Suggested-by: Matthew Wilcox Suggested-by: Peter Zijlstra Signed-off-by: Andrii Nakryiko Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Oleg Nesterov Link: https://lkml.kernel.org/r/20241122035922.3321100-3-andrii@kernel.org --- kernel/events/uprobes.c | 45 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 45 insertions(+) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 62c14df..daf4314 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -2294,6 +2294,47 @@ static int is_trap_at_addr(struct mm_struct *mm, uns= igned long vaddr) return is_trap_insn(&opcode); } =20 +static struct uprobe *find_active_uprobe_speculative(unsigned long bp_vadd= r) +{ + struct mm_struct *mm =3D current->mm; + struct uprobe *uprobe =3D NULL; + struct vm_area_struct *vma; + struct file *vm_file; + loff_t offset; + unsigned int seq; + + guard(rcu)(); + + if (!mmap_lock_speculate_try_begin(mm, &seq)) + return NULL; + + vma =3D vma_lookup(mm, bp_vaddr); + if (!vma) + return NULL; + + /* + * vm_file memory can be reused for another instance of struct file, + * but can't be freed from under us, so it's safe to read fields from + * it, even if the values are some garbage values; ultimately + * find_uprobe_rcu() + mmap_lock_speculation_end() check will ensure + * that whatever we speculatively found is correct + */ + vm_file =3D READ_ONCE(vma->vm_file); + if (!vm_file) + return NULL; + + offset =3D (loff_t)(vma->vm_pgoff << PAGE_SHIFT) + (bp_vaddr - vma->vm_st= art); + uprobe =3D find_uprobe_rcu(vm_file->f_inode, offset); + if (!uprobe) + return NULL; + + /* now double check that nothing about MM changed */ + if (mmap_lock_speculate_retry(mm, seq)) + return NULL; + + return uprobe; +} + /* assumes being inside RCU protected region */ static struct uprobe *find_active_uprobe_rcu(unsigned long bp_vaddr, int *= is_swbp) { @@ -2301,6 +2342,10 @@ static struct uprobe *find_active_uprobe_rcu(unsigne= d long bp_vaddr, int *is_swb struct uprobe *uprobe =3D NULL; struct vm_area_struct *vma; =20 + uprobe =3D find_active_uprobe_speculative(bp_vaddr); + if (uprobe) + return uprobe; + mmap_read_lock(mm); vma =3D vma_lookup(mm, bp_vaddr); if (vma) {